Vehicle external mirror housings have evolved from simple mounting structures for “wing mirrors” to receptacles for mirrors performing many functions and housing a number of components. For instance, mirror housings commonly house servomotors which are capable of rotating mirrors mounted to the housings about two axes so as to enable the driver to adjust his or her field of rear view. Also external mirror housings commonly are pivotable inward towards the vehicle side in the event of a collision with a solid object and, in some circumstances, automatically upon parking the vehicle to reduce the protrusions from the vehicle's side and its maximum width. Furthermore, equipment such as heaters, antennas and lights may also be supported by the modern external mirror housing. External mirror housings must also be shaped so as to minimize wind noise and so as to minimize drag, while providing an aesthetically pleasing external appearance. As a result, mirror housings have become larger, heavier, more complex and therefore more expensive to produce.
To achieve the functionality and performance required at a reasonable cost, vehicle external mirror housings are usually produced in plastic using injection molding techniques. Typically housings are made from shells of injection molded plastics having wall thickness in the range of 2 to 3 millimeters. Such a wall thickness has been found to provide adequate strength and rigidity.
Many different mirror housing constructions are known. Mirror housings may be formed by two mating structural components, by one cosmetic component and one structural component, or from a single cosmetic/structural component. However generally, mirror housings are produced from at least two mating components, which, when joined, form a hollow shell. Mating bosses, molded into the shells are usually provided to facilitate alignment and joining of components. Within the hollow shell is provided a mount to enable connection of the mirror housing to a vehicle bracket, which itself is attached to the side of a vehicle. In order to avoid high stresses within the plastic shell, these mounts must be designed so that they distribute load away from the mount itself. This becomes increasingly important as the wall thickness of the plastics shell is reduced.
Vehicle external mirror housings are generally made from shells having mounting and connection bosses which add to the complexity of the injection molding tooling. Furthermore, the injection molded shells, having a wall thickness of 2 to 3 millimeters take a significant time to cool resulting in a cycle time of about 50 seconds. A reduction in wall thickness not only reduces cycle times but also reduces the amount of plastics material used, reduces the cost and reduces the weight of the mirror housing.
An alternative external vehicle mirror construction for large mirrors such as those found on trucks and buses is disclosed by Canadian Patent Application No. 2198267. With this construction, a core is molded from polyurethane foam and subsequently a reinforcing layer “a few millimeters thick” is sprayed on. While this construction may have some advantages for large mirrors, it has the disadvantage that the surface finish is difficult to control with precision.
It is an object of the present invention to provide an improved vehicle external mirror that overcomes some of the problems outlined above.